When a computer system interfaces with a Double Data Rate (DDR) Synchronous Dynamic Random-Access (SDRAM) memory, a DDR controller typically manages the flow of data between the host device for the DDR controller and the DDR memory device(s). The DDR protocol specifies the transfer (read/write) of data on both the rising and falling edges of the data bus strobe (typically referred to as DQS) signals. The DDR controller typically interfaces with the DDR memory device using a Physical (PHY) interface that converts digital signals and commands from the DDR controller logic into waveforms (signals) that the DDR memory can interpret.
In order for reliable data transfer, the read/write operations in DDR SDRAM devices have to adhere to strict setup and hold time requirements. However, as the operating frequency of the DDR SDRAM device increases, the setup/hold timing requirements become more difficult to meet due to the data line skew.
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